3D Soft Tissue Laser Scanning Technology to Evaluate Soft Tissue Changes after Orthognatic Surgery

INTRODUCTION: Different technologies can be used to evaluate soft tissue changes after orthognathic surgery. Each technology comes with its own limitations, advantages, and costs. We compared 2D and 3D Soft tissue evaluation techniques. AIM: The purpose of this study is to evaluate the limitations, advantages and cost factor of two different techniques for evaluation of soft tissue changes after orthognathic surgery. METHODS: Pre surgical lateral cephalogram and laser soft tissue scan taken. Postsurgical cephalogram and laser scan taken 6 months after orthognathic surgery. Soft issue evaluation was done using Arnett and Bergman analysis. Both presurgical and postsurgical values compared to asses soft tissue changes. 2D and 3D soft tissue evaluation techniques evaluated to asses advantages and disadvantage of each technique. RESULT: Laser soft tissue scanner is an effective, more accurate, and convenient tool for soft tissue change evaluation. CONCLUSION: Advanced 3D laser scanner gives exact 3D information of a 3D object. Technique is easy, and needs less processing time. All measuring tools are incorporated in data reading software. Measurements show accuracy in micron level. Lateral cephalogram is cost effective, but it represents 2D aspect of a 3D object. Examiner level error in measurement is common in 2D soft tissue evaluation technique

Biomechanical Stress and Strain Analysis of Mandibular Human Region from Computed Tomography to Custom Implant Development

Currently computational tools are helping and improving the processes and testing procedures in several areas of knowledge. Computed tomography (CT) is a diagnostic tool already consolidated and now beginning to be used as a tool for something even more innovative, creating biomodels. Biomodels are anatomical physical copies of human organs and tissues that are used for diagnosis and surgical planning. The use of tomographic images in the creation of biomodels has been arousing great interest in the medical and bioengineering area. In addition to creating biomodels by computed tomography it is also possible, using this process, to create mathematical models to perform computer simulations and analyses of regions of interest. This paper discusses the creation of a biomodel of the skull-mandibular region of a patient from CT for study and evaluation of efforts in the area of the temporomandibular joint (TMJ) aiming at the design and development of a TMJ custom prosthesis. The evaluation of efforts in the TMJ region due to the forces of mastication was made using the finite element method and the results were corroborated by comparison with mandibular models studied in similar works

An Evaluation of Digital Methods in Reverse Engineering Using Selected Medical Applications

Student Number : 9710738R - MSc (Eng) dissertation - Faculty of Engineering and the Built EnvironmentThis dissertation investigates the use of digital modeling methods for selected medical applications. The digital methods include the design of a cranial implant, auricular prosthesis and the duplication of an oral prosthesis. The digital process includes imaging, image processing, design and fabrication steps. Three types of imaging used are contact and non-contact measurement systems and CT scanning. The investigation uses a Phantom haptic device for digital design. The implants and prostheses are fabricated using a Thermojet printer and investment casting. Traditional and digital processes are compared using four case studies on selected criteria. The conclusions of the investigation are that a digital process can be used and is equal to or better than traditional methods in prosthesis and implant design

Estimating patient-specific and anatomically correct reference model for craniomaxillofacial deformity via sparse representation: Estimating patient-specific and anatomically correct reference model

A significant number of patients suffer from craniomaxillofacial (CMF) deformity and require CMF surgery in the United States. The success of CMF surgery depends on not only the surgical techniques but also an accurate surgical planning. However, surgical planning for CMF surgery is challenging due to the absence of a patient-specific reference model. Currently, the outcome of the surgery is often subjective and highly dependent on surgeon’s experience. In this paper, the authors present an automatic method to estimate an anatomically correct reference shape of jaws for orthognathic surgery, a common type of CMF surgery

An Evaluation of Cellular Neural Networks for the Automatic Identification of Cephalometric Landmarks on Digital Images

Several efforts have been made to completely automate cephalometric analysis by automatic landmark search. However, accuracy obtained was worse than manual identification in every study. The analogue-to-digital conversion of X-ray has been claimed to be the main problem. Therefore the aim of this investigation was to evaluate the accuracy of the Cellular Neural Networks approach for automatic location of cephalometric landmarks on softcopy of direct digital cephalometric X-rays. Forty-one, direct-digital lateral cephalometric radiographs were obtained by a Siemens Orthophos DS Ceph and were used in this study and 10 landmarks (N, A Point, Ba, Po, Pt, B Point, Pg, PM, UIE, LIE) were the object of automatic landmark identification. The mean errors and standard deviations from the best estimate of cephalometric points were calculated for each landmark. Differences in the mean errors of automatic and manual landmarking were compared with a 1-way analysis of variance. The analyses indicated that the differences were very small, and they were found at most within 0.59 mm. Furthermore, only few of these differences were statistically significant, but differences were so small to be in most instances clinically meaningless. Therefore the use of X-ray files with respect to scanned X-ray improved landmark accuracy of automatic detection. Investigations on softcopy of digital cephalometric X-rays, to search more landmarks in order to enable a complete automatic cephalometric analysis, are strongly encouraged

3D soft-tissue, 2D hard-tissue and psychosocial chantes following orthognathic surgery

A 3D imaging system (C3D®), based on the principles of stereophotogrammetry, has been developed for use in the assessment of facial changes following orthognathic surgery. Patients’ perception of their facial appearance before and after orthognathic surgery has been evaluated using standardised questionnaires, but few studies have tried to link this perception with the underlying two-dimensional cephalometric data. Comparisons between patients’ subjective opinions and 3D objective assessment of facial morphology have not been performed. Aims: (1) To test the reliability of the 3D imaging system; (2) to determine the effect of orthognathic surgery on the 3D soft-tissue morphology; (3) to assess skeletal changes following orthognathic surgery; (4) to evaluate soft-tissue to hard-tissue displacement ratios; (5) to ascertain the impact of orthognathic surgery on patients’ perception of their facial appearance and their psychosocial characteristics, (6) to explore the dentofacial deformity, sex and age on the psychosocial characteristics; (7) to evaluate the extent of compatibility between the cephalometric and the three-dimensional measurements and (8) to determine if the magnitude of facial soft-tissue changes affects the perception of facial changes at six months following surgery. Results and Conclusions: C3D imaging system was proved to be accurate with high reproducibility. The reproducibility of landmark identification on 3D models was high for 24 out of the 34 anthropometric landmarks (SD£0.5 mm). One volumetric algorithm in the Facial Analysis Tool had an acceptable accuracy for the assessment of volumetric changes following orthognathic surgery (mean error=0.314 cm3). The error of cephalometric method was low and the simulation of mandibular closure proved to be reproducible. 2D soft-tissue measurements were compatible with 3D measurements in terms of distances, but angular measurements showed significant differences (p<0.05)

Making three-dimensional Monson's sphere using virtual dental models

학위논문 (박사)-- 서울대학교 대학원 : 치의학과 구강해부학 전공, 2013. 8. 이승표.The Monsons sphere and curve of Wilson can be used as reference for prosthetic reconstructions or orthodontic treatments. This study aimed to generate and measure the three-dimensional (3-D) Monsons sphere and curve of Wilson using virtual dental models and custom software. Mandibular dental casts from 68 young adults of Korean descent were scanned and rendered as virtual dental models using a 3-D digitizing scanner. 26 landmarks were digitized on the virtual dental models using a custom made software program. The Monsons sphere was estimated by fitting a sphere to the cusp tips using a least-squares method. Two curves of Wilson were generated by finding the intersecting circle between the Monsons sphere and two vertical planes orthogonal to a virtual occlusal plane. Non-parametric Mann-Whitney and Kruskal-Wallis tests were performed to test for difference between sex and in cusp number within tooth position. The mean radius of Monsons sphere was 110.89 ± 25.75 mm. There were significant differences between males and females in all measurements taken (p 0.05). This study describes a best-fit algorithm for generating 3-D Monson's sphere using occlusal curves quantified from virtual dental models. The radius of Monson's sphere in Korean subjects was greater than the original four-inch value suggested by Monson. The Monsons sphere and curve of Wilson can be used as a reference for prosthetic reconstruction and orthodontic treatment. The data found in this study may be applied to improve dental treatment results.Ⅰ. Introduction Ⅱ. Review of Literature Ⅲ. Material and Methods Ⅳ. Results Ⅴ. Discussion Ⅵ. Conclusions References Appendix Table and Figures Korean AbstractDocto

Three-dimensional assessment of facial morphology in infants with cleft lip and palate

Differential growth was demonstrated between facial features and within some facial features. In particular, the columella, nostrils and philtrum did not grow significantly after surgery, although this would be considered normal in the age group studied. Facial growth in children with UCL and UCLP was independent of the head and body growth. The presence of a cleft of the secondary palate accentuated the amount of soft tissue disruption by the cleft in the lip and nose, but not the pattern of disruption. Primary lip / nose repair had no detrimental effect on the early growth and development of the facial features. Likewise, palate repair had no discernible effect on facial soft tissue growth at age 2 years. Primary lip /nose repair had a beneficial effect on facial morphology in terms of reducing asymmetry and was most successful in the improving philtrum and nasal base symmetry, less successful in improving the nasal rim asymmetry. A possible early beneficial effect of cleft repair remote from the surgery site was noted in the reduction of upper face asymmetry in the first year of life. Residual asymmetry in the facial features did not change by age 2 years, despite increases in size with growth. Facial morphology outcomes for UCL and UCLP children in this study was generally similar at 2 years of age, despite marked differences in pre-operative facial form. However, nasal base asymmetry, upper face asymmetry and residual nostril shape deformity were significantly greater in UCLP children at 2 years of age, than in UCL children. These shape differences were not detectable by measurement of facial dimensions alone

Efficient techniques for soft tissue modeling and simulation

Performing realistic deformation simulations in real time is a challenging problem in computer graphics. Among numerous proposed methods including Finite Element Modeling and ChainMail, we have implemented a mass spring system because of its acceptable accuracy and speed. Mass spring systems have, however, some drawbacks such as, the determination of simulation coefficients with their iterative nature. Given the correct parameters, mass spring systems can accurately simulate tissue deformations but choosing parameters that capture nonlinear deformation behavior is extremely difficult. Since most of the applications require a large number of elements i. e. points and springs in the modeling process it is extremely difficult to reach realtime performance with an iterative method. We have developed a new parameter identification method based on neural networks. The structure of the mass spring system is modified and neural networks are integrated into this structure. The input space consists of changes in spring lengths and velocities while a "teacher" signal is chosen as the total spring force, which is expressed in terms of positional changes and applied external forces. Neural networks are trained to learn nonlinear tissue characteristics represented by spring stiffness and damping in the mass spring algorithm. The learning algorithm is further enhanced by an adaptive learning rate, developed particularly for mass spring systems. In order to avoid the iterative approach in deformation simulations we have developed a new deformation algorithm. This algorithm defines the relationships between points and springs and specifies a set of rules on spring movements and deformations. These rules result in a deformation surface, which is called the search space. The deformation algorithm then finds the deformed points and springs in the search space with the help of the defined rules. The algorithm also sets rules on each element i. e. triangle or tetrahedron so that they do not pass through each other. The new algorithm is considerably faster than the original mass spring systems algorithm and provides an opportunity for various deformation applications. We have used mass spring systems and the developed method in the simulation of craniofacial surgery. For this purpose, a patient-specific head model was generated from MRI medical data by applying medical image processing tools such as, filtering, the segmentation and polygonal representation of such model is obtained using a surface generation algorithm. Prism volume elements are generated between the skin and bone surfaces so that different tissue layers are included to the head model. Both methods produce plausible results verified by surgeons